A coilover is an automobile suspension device, short for "coil (spring) over strut". It consists of a shock absorber (British: damper) with a coil spring (British: helical spring) encircling it. The shock absorber and spring are preassembled as a unit prior to installation, and are replaced as a unit when the shock absorber has leaked. This provides for optimal damping without torsional loads. Some coilovers are adjustable for ride height and hardness as well using a simple threaded spring perch similar to a nut.The coilover is a basic component of the MacPherson strut suspension system, which is distinguished from other arrangements by employing a particular design of anti-roll bar as a longitudinal constraint. This was the first widespread use of the coilover in automobile suspensions. But there are other designs; the word coilover should not be considered a synonym for the MacPherson strut arrangement.Coilovers should not be confused with struts or independently mounted shock absorbers.Retrieved from "http://en.wikipedia.org/wiki/Coilover"